Network consultant Michael Biber says IPv4 is on its last legs. IPv4's 32-bit format can describe 4.3 billion unique addresses. That's not enough.

"It's one address for every two people," Mr Biber says. "Obviously not all of them have a computer . . . but there is an enormous spread of mobile phones and radio wireless in Africa and throughout Asia - Bangladesh has higher mobile phone penetration than Australia. All the new voice over IP phones and G3 mobile phones need an IP address."

Australian National University researcher Geoff Huston predicts the pool of unallocated addresses will run dry in May 2011, if current consumption trends continue. However, a "last-minute rush" as supply dwindles could see the crisis come much earlier.

Without enough addresses, the internet simply will not work. A stop-gap solution to the problem, known as network address translation (NAT), has caused more problems. "It breaks the trust in the network," Mr Biber says. "You can no longer tell if a person behind a gateway is who you think it is." This has encouraged the spread of spam and phishing attacks.

So what's the alternative? IPv6 was invented by Steve Deering and Australian Craig Mudge at Xerox PARC and uses 128 bits - 340 billion billion billion billion unique addresses. That's 6 billion addresses for every gram of matter in the earth.

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